A Secret Forest Grew for Millennia in North America Without Anyone Noticing

Cedar trees living on steep cliffs were centuries old, and no one knew.

Doug Larson was not looking for old trees. The ecologist started working on the cliffs of the Niagara Escarpment because, like the tundra where he had studied mosses and lichens, they were relatively untouched by humans. It didn't hurt, either, that his new research spot was close to his home in Guelph, Canada, a university town just over an hour west of Toronto.

Even after he and his students started studying the ecology of cliff face, it took them three years to discover a startling fact, hiding in plain sight—that the cliff's small and gnarled cedar trees were hundreds of years old. No one would have imagined that there could still be an unknown old growth forest so close to a major urban area.

“They were overtly struggling to survive, but we thought the struggle was 60 years old, not 600 years old,” he said.

The first time the idea occurred to Larson, in 1988, he did not trust it. He had been counting the rings of a tree under a microscope, and there had been hundreds. But he could be wrong, he thought: perhaps there was some explanation, other than that this diminutive tree had been alive since before Europeans reached this continent. He didn’t sleep for three days. The area where they had been working was on the outskirts of Toronto, and to find a forest that old in a major city was “heretical at the time,” he says. But the tree ring lab at the Lamont-Doherty Earth Observatory confirmed what they had found—centuries-old trees. The oldest had lived for approximately 700 years.

The Amputee, born in 1134 A.D., had its limbs cut away by a climber. (Photo: Peter Kelly)

Once, it would not have been so uncommon to find trees that had lived for hundreds of years. In southern Ontario, there would have once been aged oaks, but in most places, those trees have long since been felled to make way for farms or to serve as lumber. What we now call “old-growth” forests are simply communities of trees that have been allowed to continue on undisturbed while most of the forest around them has been thinned or cut down entirely. In North America, even places that look thickly forested to us now are often full of relatively young trees, regrown on patches of land that were farms not so long ago.

For eastern white cedar trees, the cliffs had been a refuge. The Niagara Escarpment is a steep slope that curves around the Michigan basin, from Wisconsin, across Michigan’s upper peninsula, and down across Ontario, until it hits New York State and Niagara Falls. It’s not an easy place to live, but for the birds, snails, spiders and plants that have figured out how to survive there, it has some advantages. There are few predators, no fire, no floods, and hardly any competition.

“There is something wonderful about animals and plants that depend on cliffs,” says Larson. “They’re there because no one else can live there. They have a physiological toughness that allows them to sit out in these places that nothing else can touch, and they thrive there.”

The trees that survived in this way for hundreds of years contorted themselves into incredible shapes. One, nicknamed “The Snake,” slithered down the cliff face with roots crammed into a horizontal crack about a fifth of an inch wide. “If you were able to take the cliff apart, the roots would look like a carpet, a half-centimeter-wide, flat root mass going back into the cliff face,” says Peter Kelly, who worked with Larson to study the trees and the cliffs for 20 years. Another, 875 years old, hung upside down and couldn’t be seen except by a person dangling from ropes down the cliff. When they expanded their area of inquiry to the U.S. and Europe, Larson and his collaborators found one of the oldest trees in the eastern U.S., an 820-year-old eastern red cedar on a cliff near Green Bay. In France, they found a tree that had been alive when Roman occupiers left France. In Canada, they found one tree that they estimated to be more than 1,800 years old when it died and that is "arguably the oldest tree ever documented" in the country, Larson and Kelly wrote.

The Ancient One. This tree was born in 688 A.D. (Photo: Peter Kelly)

Old trees are not necessarily tall trees, as is the case with Larson’s discovery. They might be 20 or so feet in length, at most, but twisted and deformed so that they did not stretch tall. The oldest trees would often have sharp taper, says Kelly. Their bases would be thick and gnarled. They’d have dead branches still hanging on. A branch might keep clinging to the tree for decades after it died. In places, the bark had been worn away, down to the bare wood. The top of the tree was usually dead or broken off, and a side branch had taken over as the main growth, pulling the tree in weird, compelling shapes.

Many of the oldest trees were also hanging upside down. At some point, they had been knocked over, or the place they were growing on had shifted in a rockfall. The tree had been flipped, but it hung on, with at least part of its root structure, and kept growing.

It wasn’t a coincidence that these aged trees were cedars. Most trees use their root systems to feed the entire tree, so if one part of the roots are damaged, the whole tree suffers. In cedars, each part of the roots system is connected to a certain part of the tree. If those roots die, that part of the tree dies, while the rest continues on. In Larson’s lab, they showed how stark this mechanism could be by feed three different sections of roots water dyed three different colors. When they peeled back the bark, the tree looked like a barber shop pole, with the colors swirled separately up its length.

On the cliffs, that meant that if part of the roots system lost access to water or was damaged, the rest of the tree just kept growing. One side of a tree might show 10 years of growth; the other might continued living for a thousand.

The Mosquito tree is more than 500 years old. (Photo: Peter Kelly)

Many of these trees live in areas that are thick with people; the sites where Larson and Kelly worked might be half an hour away from their homes. “I would wake up in my bed, in Guelph, and by noon I could be touching things that no human had ever touched before,” says Kelly. The trees' choice of dwelling, on the steep cliff, kept them safe from people for centuries, and even today, they’re not formally protected in any way.

They are not invincible, though.“When it comes to trees, you always have to be worried,” says Kelly. Bugs and blights have wiped out whole forests of trees; the climate is changing, and perhaps these trees won’t do as well under new conditions. There was one cliff forest that Kelly found where the trees had all died, 140 years ago, in the heat of a fire. Many of the old trees they had found showed no evidence of rot; this cliff face had simply become a graveyard of ghost trees.

These centuries-old cedars, though, show no signs of angst. “They just keep bouncing back,” says Larson. They don’t need to be bigger than they are. They produce seeds; they reproduce. They continue on.